A porous electrolytic composite membrane for electrochemical energy systems, such as alkaline fuel cells, metal-air batteries and alkaline electrolyzers, comprises a porous polymeric material and nanomaterials. The polymeric material is preferably polybenzimidazole (PBI). The nanomaterials are preferably functionalized or non-functionalized. The nanomaterials are preferably titania nanotubes and/or graphene oxide nanosheets. The membrane further comprises an electrolyte solution, such as KOH. A method of preparing the membrane is also provided.